I would appreciate any input from you guys regarding the range of bolt head sizes for the No1MkIII rifle.

I want to know the measurement between the bolt head face and the rear shoulder where it contacts the bolt body.

I ask this because my No1 rifle is close to the limit of the Field gauge and I would like to try and bring it back to the No Go gauge if possible. Also the original bolt head on this rifle seems to slightly off square, measuring 0,638" one side and 0,636" the other. I have a couple of bolt heads; 1 is unused 0,638" and parrallel, but doesn't clock in.

Were these heads all the same size then machined for fit? or did they have different sizes like with the No4 version?

I have only 3 303 bolt head. i honestly feel i have another but i cant find it..They were measured two minutes ago by me using starrett 0-1"mics.626 .629 .631" and my 22 trainer (really a no2 bolt head but same as a no1) is .631"

i believe they were all the same size and hand filed to fit. one of mine if off side to side by .001" but all four of them clock within like 3 degrees past on both my bolts.

My 22 trainer has a 0.060 thick plate brazed on the face of the bolt head. Then you can see where it was filed to size.

The No1 didn't have a range like the numbered versions the No4 had.There was just one (loong) one & it was filed to fit as needed. That means you'll need to either find one filed to the length you need, or get a longer one & shorten it.The not clocking is the bigger problem, the thread starts varied a lot.

Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)

It would be hard to reharden without knowing the make up of the metal. it would need carbon in it witch it probably has. its probably hi-carbon steel, but less then todays 4140, but not knowing the carbon content its more of a trial and error kind of thing to get the right hardness

they are hardened, i just tried a file on it

but we are in luck, i have a starrett RC hardness tester at work, tomorrow ill check two bolt heads and let you know how hard they are. just a guess by the file test i guess around 40rc, standard 4140 is 32rc, tool steels get hardened from 40-70rc

you would have to soften one to file to to size. then carbon oil quench, then temper it back off to not breakable/dent instead of chip

So if my replacement bolt head is unused and unfitted; I suppose that it is the longest available. I would like to confirm what is the maximum length to be sure. I have a couple of others; the original and one seconhand one (that is shorter) both have the notch cut out at the end of the thread. Both of these clock in ok. The other two do not have the notch cut out at the end of the thread and neither of the will clock in. Both stop short as if binding on the last thread. But even the slight gap that's left when it locks up would not be enough to allow it to reach the correct position.I may look for another bolt body to test. Although that opens another can of worms fitting the bolt.This rifle shoots well now, after having been through lots of adjustments. But now I've bought theOakie gauges I have confirmed what I had suspected is that the head space is on the limit. As I reload; I prefer to reduce it a bit. Even a couple of thou would make a difference.

"So if my replacement bolt head is unused and unfitted; I suppose that it
is the longest available. I would like to confirm what is the maximum
length to be sure."That should be correct.Surprisingly I have had a hard time finding the measurement. I'm still looking though.

Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)

Wow, harder then i thought. i tested the bolt face on two bolt heads they were 51rc and 48rc. the 48rc was a pitted bolt head the 51rc was near perfect condition. now i have small dents in them haha oh well. it was worth it.

OK, I still can't find a length for you, but all is not lost.A new, unfitted (& so longest) head has an "S" stamped in it I think on the front face of the extractor lug. Not sure how much that helps but at least you know you're looking for an "S" stamped bolt head.

Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)

Are you having a problem with head spacing on a Mark III? I have a number of them and haven't encountered any problem. Bolts are pretty much interchangeable between rifles. It's the No. 4 Mark I, that they got creative with. If your reloading ammunition shot in the No.4 Mark I, and using it in the Mark III you could possibly encounter a case head separation. The problem is the head space in the No.4 Mark I, it was fired in. You have to watch the area just ahead of the case head for signs of thinning from sizing and resizing, especially if its been fired in a No.4 Mark I. The older Mark III had looser chamber. This allow the British to use thinner walled brass. When the Canadians attempt to fire the British brass in the Canadian made Ross rifles, it expanded such that it would jam in the chamber. So if you have had a case of head separation in a Mark III it the larger chamber allowing a weaken area of an over used case to over expand.

I have seperate ammo for my No1MkIII* and my No4 Mk1/2 rifles. The head space on the No1 is very close to the limit of the field gauge which is 74 thou, fails the armourers No-Go which is 70 thou.I just want to try and get it back to the 70 thou mark. I suspect it's probably around 72 or 73 thou at present. I am using the OKIE gauges instead of my old DIY method, and it's proved a worthwhile investment because I was close but not really accurate enough with the DIY system.

To my knowledge the Mk III only has one length of bolt-head. It maybe the gun was re-barreled at one point, and the new barrel was't set deep enough. Are you experiencing any blow back? You can sometime compensate for the difference in head space by not running the brass as deep into the sizing die, you may of course have to readjust the depth of your primer punch.

Well i know your trying to fix your rifle properly. but there is always the option of head spacing off the sholder instead of the rim.

My mauser has 0.040 head space wih the rim THERE lol. so i have to either seat my cast bullet out far enough to hit the rifling, in return holding the rim back against the bolt face witch fire forms the sholder to its new location. now they head space off the sholder and are tight when i close my bolt.

A better option may be to use rubber orings on the base of the case before the rim to hold them out to you bolt face until the sholder is moved.

But hopefully you are able to find a longer bolt head or maybe try anothr bolt. there are a few options none are as ideal of the propper size bolt head.

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